GNU bug report logs - #12447
24.1.50; Stuck in garbage collection on OS X

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: Eli Zaretskii <eliz <at> gnu.org>
Cc: tracker <at> debbugs.gnu.org
Subject: bug#12447: closed (24.1.50; Stuck in garbage collection on OS X)
Date: Sat, 22 Sep 2012 13:22:01 +0000

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Your message dated Sat, 22 Sep 2012 16:18:56 +0300
with message-id <83ehlukxfj.fsf <at> gnu.org>
and subject line Re: bug#12447: 24.1.50; Stuck in garbage collection on OS X
has caused the debbugs.gnu.org bug report #12447,
regarding 24.1.50; Stuck in garbage collection on OS X
to be marked as done.

(If you believe you have received this mail in error, please contact
help-debbugs <at> gnu.org.)


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From: Harald Hanche-Olsen <hanche <at> math.ntnu.no>
To: bug-gnu-emacs <at> gnu.org
Cc: jan.h.d <at> swipnet.se
Subject: 24.1.50; Stuck in garbage collection on OS X
Date: Fri, 14 Sep 2012 23:08:19 +0200 (CEST)

This concerns emacs built with --with-ns from trunk on OS X.

To start with the symptom: Emacs seems to freeze, and spends a lot of
CPU time. Taking a sample with Activity monitor appears to indicate a
very deeply nested mark_object calls; from this I conclude that the
problem appears to happen in GC.

How to trigger the symptom: I always got it by trying to send an email
message with a large attachment. My mail client of choice is Mew, but
I suspect that any activity triggering garbage collection will also
trigger the bug.

After bisecting, I come to the conclusion that this revision is to
blame:

revno: 109470
committer: Jan D. <jan.h.d <at> swipnet.se>
branch nick: trunk
timestamp: Mon 2012-08-06 18:09:02 +0200
message:
  * keyboard.c (timer_check_2): Add break so timer_check returns next timeout.

That revision only adds a single line of code. I also find that the
bug disappears if I patch the current tip of trunk (revision 110013)
as follows, which undoes revision 109470:

=== modified file 'src/keyboard.c'
--- src/keyboard.c	2012-09-13 02:21:28 +0000
+++ src/keyboard.c	2012-09-14 19:12:15 +0000
@@ -4484,7 +4484,6 @@
 	    }
 
 	  nexttime = make_emacs_time (0, 0);
-          break;
 	}
       else
 	/* When we encounter a timer that is still waiting,


I suppose the break was added for a good reason, so this is probably
not the right thing. But it does cure the present problem.

(This bug is also discussed on the emacs-devel list, in the thread
titled "Emacs seems awfully unstable on OS X lately".)

There seems to be a second bug, introduced later, that causes crashes
(as opposed to hangs). I mention this because the second bug could
interfere with attempts to work on this one. I will endeavour to track
down the other bug as well.

- Harald

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From: Eli Zaretskii <eliz <at> gnu.org>
To: Chong Yidong <cyd <at> gnu.org>
Cc: hanche <at> math.ntnu.no, 12447-done <at> debbugs.gnu.org, dgutov <at> yandex.ru
Subject: Re: bug#12447: 24.1.50; Stuck in garbage collection on OS X
Date: Sat, 22 Sep 2012 16:18:56 +0300

> From: Chong Yidong <cyd <at> gnu.org>
> Cc: dgutov <at> yandex.ru,  hanche <at> math.ntnu.no,  12447 <at> debbugs.gnu.org
> Date: Fri, 21 Sep 2012 22:26:18 +0800
> 
> Eli Zaretskii <eliz <at> gnu.org> writes:
> 
> >> If I understand correctly, js2-mode (prior to the workaround) assumed
> >> the new behavior: it called run-with-idle-timer from inside the idle
> >> timer, with the same delay, with the intention of scheduling for the
> >> next period of idleness.
> >
> > I have no idea what js2-mode wants to do.  What I wrote above was
> > based on my limited reading of the code fragments posted to that bug.
> 
> OK, I guess your approach is fine.  Please go ahead and commit your
> patch when you're ready, and amend the docstring of run-with-idle-timer
> as Dmitry suggested.

Done in trunk revision 110138.  I'm therefore closing this bug.

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